The present invention relates to a low noise tire in which pattern noise caused by axial grooves is suppressed.
From the point of view of environmental pollution as well as ride comfort, automobile noise, especially in high-speed running, is a problem to be solved.
The main part of the automobile noise is a tire noise, and the main part of the tire noise is pattern noise. Such pattern noise is generated as follows.
The tread groove volume, specifically the axial groove volume is greatly and periodically changed when contacting the ground and leaving the ground during running, which vibrates the air and therefore a pressure wave of the air is generated as noise.
Generally, there is a remarkable peak in the sound energy spectrum around the frequencies determined by the circumferential pitches of the tread pattern and the tire rotating speed, and when the peak value is large. It makes the generated sound very noisy.
Therefore, to lower the pattern noise, methods such as variable pitching methods have been proposed.
In the variable pitching methods, in order to lower the absolute value of the peak, several different pitches are arranged in the circumferential direction of the tire in a special manner to disturb synchronism of the noise pulses generated from the tread pattern and thereby to disperse the noise sound energy into a wide frequency range.
However, the optimum pitching is not always optimum in view of other tire performances, and often deteriorates tire performances. For example, tread elements with different pitches have different rigidities, which is liable to cause uneven tread wear whereby the tire has a short wear life, and further sometimes unfavorably affects the vibration characteristics such as RFV and RRO.